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Old July 21, 2014, 11:17 AM   #1
J270
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243 Win in the wind

I took my wifes 243 out yesterday. This gun shoots well under MOA. My groups were not up to its useual par. The conditions were real windy. My question is will wind have a factor on a 100 gr bullet at 100 yards. I am a 270 win guy and I dont have the experience with the 243. Just wondering
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Old July 21, 2014, 11:34 AM   #2
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Wind is a factor on anything at 100 yards if the wind is strong enough

with maybe the exception of extremely high BC bullets like 300 grain .338 and 900 grain .50 cal boat tails, which drift just under an 1'' @ 100 yards in a 90 degree 10mph crosswind, most bullets will suffer from some wind deflection at 100 yards

It's almost completely dependent on the bullet's ballistic coefficient. While 100 grain .243 grain bullets don't usually have bad B.C's, they don't quite hold up to the heavy for caliber 6.5mm 6.8mm and 7mm boat tails.

A 100 grain .243 VLD bullet should have just over an 1'' of wind drift in a 90 degree 10mph cross wind. If you're using a flat based bullet, or a bullet with a less aerodynamic shape, you will suffer from more wind drift.
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Old July 21, 2014, 03:02 PM   #3
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Absolutely it does. Depending on how windy it is can influence the bullets flight and the shooter himself. Some of my worse days at the range are when the wind is blowing the hardest even though I know to compensate for it and how much to compensate. I've come to believe people who shoot well in the wind are more than marksman, they're magicians
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Old July 21, 2014, 03:10 PM   #4
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I had posted the same question a couple weeks ago... 10mph crosswind was blowing my 7X57 off as much as 2 inches at 100 yards... .243 could be more
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Old July 21, 2014, 06:07 PM   #5
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I try not to shoot for groups when the wind is switchy and strong, but if it's fairly uniform, I bring up to 5 wind flags with survey tape tails to help me dope the wind.

Actually, I look for repeated conditions, both in direction and speed and try to shoot the same condition whenever possible. A three or five shot group can usually be shot with close to the same conditions, not so with a 25 bull rimfire benchrest target. We try to limit shots to two or three fairly uniform conditions when shooting matches.

If a condition isn't one of the previous known ones, we shoot a sighter or two and log that condition if it stays uniform.

I made my own wind flags, using plastic sign board and wire coathangers. Cheap music stands with the angled top cut off and a bearing made from a 1/4" carriage bolt with a hole drilled in the top, a bit larger than the coathanger wire serve as flag stands.

In a pinch, a broomstick driven in the ground with a hole drilled in the top and piece of brazing rod bent on a 90* angle with a loop on the end to hold a piece of survey tape tied to it, will work reasonably well.
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Old July 21, 2014, 08:23 PM   #6
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At 100 yards, using similar shaped bullets, .243 Winchester and .270 Winchester will only show miniscule differences in wind drift.

Reading wind is an art. I can deal with a simple cross wind easy enough. Sometimes I just say heck with it and shoot. When every wind flag is headed a different direction, I just give up and shoot.
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Old July 21, 2014, 09:27 PM   #7
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Depends on the speed of the cross wind. For the most part no not at 100 yards, at 5 to 10 mph a 100 grain 243 will perform the same as a 130 grain 270. At 25 MPH micro bursts all bets are off on any weight bullet, but at 250 yards the 100 grain bullet will be more affected then the heavier 130 grain bullet will. They will both still be affected just at different amounts, and the faster the bullet (243) will be affected more.

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Old July 21, 2014, 09:31 PM   #8
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Do you hand load ammunition or do you buy factory? If you buy factory did you change your ammunition. Wind can throw off groups at 100 but it isn't the only thing that can affect your groups.

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but at 250 yards the 100 grain bullet will be more affected then the heavier 130 grain bullet will. They will both still be affected just at different amounts, and the faster the bullet (243) will be affected more.
Not really how a bullet is affected by wind is determined by ballistic coefficient or BC for short. A 100 grain .243 could possibly have a better BC than a 130 grain .277 bullet and be less affected by the wind. Weight has little to do with how a bullet is affected by the wind except for the fact the heavier a bullet is usually means it's longer thus giving it a better BC for its caliber.
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Old July 21, 2014, 09:44 PM   #9
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Quote:
Originally Posted by J270
I took my wifes 243 out yesterday. This gun shoots well under MOA. My groups were not up to its useual par. The conditions were real windy. My question is will wind have a factor on a 100 gr bullet at 100 yards. I am a 270 win guy and I dont have the experience with the 243. Just wondering
All bullets are effected by wind. Your .270 is no exception. You can use any of the various and plentiful ballistics calculators available online to give you the numbers.

I like JBM Ballistics.
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Old July 21, 2014, 10:45 PM   #10
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Jim 243, the statement about the faster bullet being effected more is not really correct. All other factors being equal, the less time a bullet spends in flight, the less it is pushed by wind.
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Old July 21, 2014, 10:50 PM   #11
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Quote:
Not really how a bullet is affected by wind
I'm sorry you are saying that the faster speed bullet (lighter) is not getting more dynamic wind resistance to it's path?? Gee maybe we should stop using 300 grain bullets for the 50 cal. (NOT)

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Weight has little to do with how a bullet is affected by the wind
Let's just suspend the law of physics, since it has no place on this forum.

Here's a little test for you un-believers, take your 223 and 30-06 to the range and shoot at 300 yards without changing your point of aim and see which one hits closer to your original point of aim (no adjustment for wind).

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Old July 21, 2014, 11:30 PM   #12
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Quote:
Let's just suspend the law of physics, since it has no place on this forum.

Here's a little test for you un-believers, take your 223 and 30-06 to the range and shoot at 300 yards without changing your point of aim and see which one hits closer to your original point of aim (no adjustment for wind).
Jim, we aren't ignoring the laws of physics. However, you are over simplifing things too far. Bullet shape and not weight determines how well it will slip through the wind. It's still all about BC and time of flight or TOF.

If you have two identical BC's regardless of weight the bullet with the fastest TOF will have the least deviation caused by wind. Hypothetically if you could have a 55 grain .224 bullet going 3000 fps and a 180 grain .308 bullet going 2800 fps both with a BC of say .300 the 55 grain bullet is going to be less affected by wind since its time to target will be shorter regardless of distance. Because their BC is exactly the same they react to the wind the same but the faster bullet has less deviation and stays faster.

The 55 grain bullet will drift 1" in a 10 mph crosswind at 100 yards and the 180 grain bullet will drift 1.1" in the same wind and distance. The thing is the little 55 grain .224 caliber bullet usually only has a BC in the .200's, and the 180 grain .308 are usually .400+ in the BC department. It has little to nothing to do with the weight in grains of the bullet other than lenght. That is why your .223 is more affected by the wind than a
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Old July 21, 2014, 11:43 PM   #13
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Quote:
Bullet shape and not weight determines how well it will slip through the wind.
And what shape might that be, the one you loaded into your rifle, or the one that you applied 35 to 50 thousand psi and 2,000 degrees of heat to as you mis-shape the BC to conform with your lines and groves????????????????????? Common sense goes a long ways, but not here!!!!!!


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Old July 22, 2014, 07:39 AM   #14
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This is the data from my records regarding the 243 vs. 270

I don't shoot 100s this is the 87 gr. Berger VLD vs Hornady 130 IB.

The velocity of the two is about the same, 2900 fps.

At 100 yards with a 10 mph full value wind the drift at 100 yards is

243 .7 inches
270 .6 inches
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Old July 22, 2014, 08:00 AM   #15
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Quote:
Originally Posted by Jim243
And what shape might that be, the one you loaded into your rifle, or the one that you applied 35 to 50 thousand psi and 2,000 degrees of heat to as you mis-shape the BC to conform with your lines and groves????????????????????? Common sense goes a long ways, but not here!!!!!!
Both bullets will be "deformed" by the rifling.

There's really no sense in arguing about it, it's a matter of physics.

Load your choice of bullets and speeds into a ballistics calculator and see what happens. There are even some calculators that will compare two bullets.

If you pick twp bullets that have as close as possible to identical BC and give them the same speed, you'll have as close as possible to the same trajectory and wind drift. For instance, a .270 110gr Nosler Accu-tip and a .243 90gr Nosler BT both have BCs within 0.005 of 0.370. Give them the same speed and they drop with 0.1"-.2" all the way to 500 yards and less than 0.4" difference in drift at 500.

The only thing that matters to trajectory and wind drift is BC and speed. If BC is the same, faster is always better. Weight only matters within the same caliber, since it changes the BC.
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Old July 22, 2014, 11:32 AM   #16
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Well, "time of flight" is by far the largest factor affecting the amount of wind drift (although I think the plain old weight of the bullet has a small to moderate independent effect - ??). The reason TOF is so important is just that this is the amount of time that the wind has to "work on" moving the bullet sideways.

But TOF is affected, in turn, by *both* velocity and BC (which these two factors vary inversely for the most part, and BC affects velocity loss rate after the muzzle, making them 'dynamically-interdependent' as well) - both are important.

As with drop, under about 350-400 yards, velocity is the more important factor, but after that, BC is the more important factor of the two.

Now, BC is slightly more important to wind drift, relative to velocity (at long range), than BC is important to drop, relative to velocity (at long range) - but at shorter ranges, I'm not sure whether the same is true (that BC is slightly more important for drift than for drop under say, 350 yards).

But nonetheless, velocity is by far the most important factor in time of flight under 350 yards or so (even if BC is a slightly relatively larger factor for drift than for drop at those ranges, if that makes sense), and thus the most important factor in both drift and drop, at these shorter ranges.

A speedy, low-BC .22-250 will drift much less under 400 yards than a .700 BC .338 VLD bullet doing 1000 fps from the muzzle, I do believe. Which is somewhat counter-intuitive, since the intuition "feels" that sheer independent weight should play a larger role than it does...at least my intuition.

Now for a really, *really* poor BC bullet (say, under .200ish), which also typically tend to be light as it turns out, change that tipping point from '350-400' yards to around 300 yards, at which BC takes over the more important role for TOF.

By the way, if I'm not mistaken, the reason that sheer weight has such a small effect is that the heavier the bullet is, the (typically) larger it is, proportionally, and the larger it is, the larger "side profile" or "side profile area" it has, which is simply more bearing surface for the same velocity of wind to work against. So they *mostly* cancel each other out, making it a small factor, but the reason it's not completely canceled out is due to various bullet materials, and the average mass/density per size, or density per side profile. A tungsten bullet will drift less, ceteris paribus, than a copper or mixed lead/copper one, since it's simply heavier with the same "side profile surface area". But it's heavier so going slower (i.e. ceteris paribus isn't reality), so that increases TOF, so that's a cancellation effect too. Which gets us back, always, to TOF, as the main factor, which is comprised solely of the interplay between muzzle velocity and BC.

As far as BC with "deformed" bullets - of course, as pointed out, ALL bullets become deformed, so BC is by definition what they do in such a 'deformed' state, which is why BC isn't a purely theoretical, mathematical calculation. It can be estimated on a new bullet design on a computer, but ultimately can only be established through actual measurement (calculating TOF, drift, and drop, with a known velocity, to work backward to come up with BC), and even then, BC varies some through different velocity ranges. You can't just "measure" BC in a theoretical vacuum or with some magical tool.

I'm not sure how actual BC is measured, but I'd bet that it's a tedious process of shooting at many different ranges with a known muzzle vel, known wind speed, and measuring TOF, drop, and drift to start working backwards by plotting points on a graph, then having the software come up with a curve function formula for the plots. Just the tools and process for measuring TOF are surely expensive and intricate, I'd guess (high speed cameras? sophisticated sound timers which can hear both the report and bullet impact?) Or can you calculate TOF by simply measuring drop/drift with known vels, without knowing BC, of course, the ultimate question you're trying to answer?

Or in the case of some bullet makers, dispense that all that hard work and just make up a BC.
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Old July 22, 2014, 12:00 PM   #17
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Wind deflection is greater when wind is stronger closer to the muzzle than the target. There's greater effect because the angular deviation may be the same, but due to the distance to the target, the same angle produces more deviation at the target. Deflection at the same wind velocity is less nearer the target.

Think about a 30-60-90 degree triangle on a sheet of paper. The shortest side is the target and the next shortest is the line of sight. The long-side (hypotenuse) is the (simplified) deflected bullet path caused by wind at a point along the line of sight.

If another short-side line is drawn closer to the "muzzle" the short side (deflection) becomes shorter. That represents the same wind velocity, but closer to the target.

That's why shooters should pay more attention to wind flags closer to the muzzle than to the target.
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Old July 22, 2014, 02:30 PM   #18
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Quote:
Well, "time of flight" is by far the largest factor affecting the amount of wind drift (although I think the plain old weight of the bullet has a small to moderate independent effect - ??). The reason TOF is so important is just that this is the amount of time that the wind has to "work on" moving the bullet sideways.
Really?

.338 whisper- 300 grain VLD bullet at 1050fps. ToF @ 500 yards = 1.58s
Drift = 13.91'' with 10mph 90 degree crosswind.

In same conditions

.223 55 grain Nosler BT @ 3240fps. Tof @ 500 = .66s
Drift = 32.88''


@ 100 yards

.223 ToF =.1s
Drift = 1.48''

.338 whisper
ToF = .31
Drift = 1.02''

.338 spent more time in the wind, at both ranges, and had less drift, at both ranges., at least with this particular ballistics calculator. The BC I used for the 300 grain VLD was .734 G1 which is conservative compared to Berger's 300 grain advertised at .808 G1 BC
I used Nosler's G1 data for .223
If someone wants to do tests with G7 Instead of G1 they're welcome to, I don't think results will be much different, though.

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Old July 22, 2014, 03:13 PM   #19
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Well, I guess I'm wrong. Hmmmm. Thanks for correcting me.

The 500 yard example I expected (because BC makes a bigger difference out that far, as I mentioned), but the 100 yards result I didn't. Back to the drawing board. Very interesting. Drift is quite different from drop, ain't it? Depending much more on BC (and other factors) than TOF and velocity (compared to drop). Truly bizarre. BC doesn't reduce the "side-al area", so I can't figure out why this is - must be that sheer weight plays a larger role than I thought.
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Old July 22, 2014, 03:48 PM   #20
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Quote:
Originally Posted by Unlicensed Dremel
Depending much more on BC (and other factors) than TOF and velocity (compared to drop). Truly bizarre. BC doesn't reduce the "side-al area", so I can't figure out why this is - must be that sheer weight plays a larger role than I thought.
Forget about weight, bullet weight has nothing to do with how a bullet reacts in the wind. Weight is a byproduct of bullet design only. As in the case of wind tunnel testing, most of them are done with models built to scale because large wind tunnels are cost prohibitive. They can use models to scale because they'll react the same way to the wind as the larger car, plane, or whatever they want to wind tunnel test.

Think of it the same way with bullets. If you have a bullet that has a BC of .500 and have a 6mm, .308, and .50 calibers, if you fire them at the same speed in the same wind conditions they'll all have for all intents and purposes identical trajectories. TOF is only important if the bullets of the same BC are fired at different velocities.

Simply put the more aerodynamic the bullet the better it will do in the wind regardless of weight. If weight was essential to winning the battle against wind the trend would be to larger calibers in long range competitions and not to smaller. There is a reason why 6.5 and 6mm are becoming more popular in long range shooting competitions where not restricted by rules.
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Old July 22, 2014, 04:40 PM   #21
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Quote:
Originally Posted by taylorce1
Forget about weight, bullet weight has nothing to do with how a bullet reacts in the wind.
It's all about BC but the formula for BC includes the bullets mass (weight) so it's not really that it has nothing to do with it.

Sort of like kinetic energy is different than speed but the formula includes speed, so speed DOES have something to say about kinetic energy.

It's not the weight that matters, independently, but the weight is a factor because it influences BC.
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Old July 22, 2014, 05:35 PM   #22
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Brian, yes mass is used to figure BC. However, since we aren't calculating for BC but using known BC weight isn't important right now. Weight like I said is a byproduct of bore diameter and scale of the bullet. To get a high BC bullet your going to have to make a long bullet and that requires more material so naturally the bullet is going to be heavier regarless of material used to make the bullet.

Here is a good article by Brian Litz over on Long Range Hunting. Basically he states that to get a bullet to match the 6.5mm 142 grain Sierra MK you can scale down to a 90 grain .223 and up to a 220 grain .308 Caliber bullet to match the BC. So for intents and purposes weight doesn't matter except to get the desired BC a person wants to shoot.

This is where bullet shape becomes important because not all weights are created equal. A 180 grain round nose bullet isn't going to have the same BC as a 180 grain spitzer boat tail bullet, so it will be affectd by wind differently even though they weigh the same. So simply put weight doesn't matter only BC does when your talking about bucking wind.
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Old July 22, 2014, 11:46 PM   #23
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This is from Bryan Litz on picking best bullet.

http://appliedballisticsllc.com/ball...s/bullet-data/
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